Letrozole

Letrozole is a potent, cell-permeable inhibitor of aromatase (IC50 = 2 nM).{23490} It inhibits proliferation of estrogen receptor-positive (ER+) MCF-7 cells when used alone at concentrations ranging from 0.1 to 100 nM and when used at a concentration of 10 nM in combination with testosterone or 4-androstene-3,17-dione.{46076} It also reduces matrix metalloproteinase-2 (MMP-2) and MMP-9 levels in MCF-7 cells when used at a concentration of 10 nM. Letrozole (10 µg per day) reduces tumor growth in an MCF-7Ca ovariectomized-mouse xenograft model.{46077} Formulations containing letrozole have been used in the treatment of postmenopausal breast cancer.{23489}